Transcript DMS/PS simulations

GAIA SWG
SWG
&
DMS/PS simulations
C. Babusiaux, X. Luri, E. Masana, F. Arenou
April 19 2002
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GAIA SWG
SWG Kick-Off meeting – Cambridge 11-12 March 2002
GOALS
• Involve the GAIA community in the activities of the SWG
• Organise the work and set up a coordination strategy
• Define priorities and needs for simulations
• Define a schedule for simulation activities
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GAIA SWG
Community involvement:
task list
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GAIA SWG
WP 2000 Common tools
Priority
WP 2100
Universe Models
WP 2110
D. Hestroffer / F. Mignard
WP 2111
Ephemeris
4
WP 2112
Minor Bodies
2
WP 2120
Galactic objects
WP 2121
Field stars F. Figueras / M. Haywood / A. Robin
+
WP 2122
Multiple stars
+
WP 2123
Variable stars
WP 2124
Peculiar stars
3
WP 2125
Extrasolar planets M. Lattanzi
3
WP 2126
Microlensing
2
WP 2127
Stellar clusters
2
WP 2128
Diffuse objects
3
WP 2129
Reddening model R. Drimmel
3
WP 2130
F. Arenou / S. Soderhjelm
F. Figueras
W. Evans / V. Belokurov
+
Extragalactic objects
WP 2131
Resolved galaxies
2
WP 2132
Unresolved galaxies
1
WP 2133
Quasars
3
WP 2134
Supernovae W. Evans / V. Belokurov
2
Relativistic model A. Vecchiato
3
WP 2140
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Solar System
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GAIA SWG
Organisation of the work
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GAIA SWG
Proposed structure of GAIA simulator
Common toolbox
GASS
GIBIS
Telemetry
simulations
Pixel-level
simulations
Cater for the “official” mission simulation needs
• Mission design (2002-2005)
• Preparation of data reduction (2002 )
• Preparation of scientific exploitation (2002 )
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Specific simulations for
scientific purposes
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GAIA SWG
Proposed organisation of development
CORE TEAM
• Coordination
• Maintenance & development of
common toolbox
• Ensure that mission needs are
covered
GASS TEAM
GIBIS TEAM
• Simulated Telemetry
• Simulated images
Specific simulations
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GAIA SWG
Working tools
• UML (Unified Modelling Language)
Design tool to build software systems
• Java
Object oriented, portable language
• CVS (Concurrent Versions System)
Development tool for maintenance of source code
See http://www.cvshome.org/
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GAIA SWG
Common tool box & data generators
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GAIA SWG
Integration of contributions
• Contributions provided by the community
• Integration into the system is a responsibility of the Core Team
• A programming interface, conventions & procedures will be
developed
• Documentation should be provided/developed in parallel with the code
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GAIA SWG
Status
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GAIA SWG
The GAIA System Simulator (GASS)
The aim of the GASS is to simulate GAIA telemetry (observation +
satellite HK data) using models of the objects and instruments.
The GASS will provide realistic data for:
• Predictions to be used for mission design.
• Filling of test databases (e.g. the GDAAS database)
• Testing of algorithms (e.g. cross-matching, telemetry compression,..) and
reduction software (e.g. core processing).
• Evaluation of mission performances, in particular for some peculiar objects
(binary stars, NEO’s, extrasolar planets,...)
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GAIA SWG
GASS - Simulation Process
•
Simulation of the objects visible along the scan of the instruments. For
each object and epoch the program simulates position, kinematics and
photometry. This step includes an Universe model and the scanning law
and orbitals parameters of the satellite.
•
Transformation from sky coordinates to instrument coordinates. This step
includes the geometry and the optics of the instrument, together with the
configuration of the field of view (FOV).
•
Simulation of the observational process according to the instrumental
parameters: detection, acquisition of data and telemetry. This step
includes a model of the observational process.
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GAIA SWG
Background
Reference
Universe
Objects
Apparent
Sky
Snap-shot
(t1,t2)
Scan law
Attitude
Efemeris
etc.
Raw
data
Telemetry
Instruments
Noise
etc.
Satellite &
instrument
model
Housekeeping
data
GAIA
DB
GASS activities
Data processes:
Reduction & calibration
Scientific exploitation
etc.
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GASS - Current status
• Reference Universe:
• Sun & Earth: the simulator implements a very simple algorithm to calculate
ephemeris for the Sun and Earth. No other solar system bodies are yet
considered.
• Galaxy: the Galaxy model from Torra et al. (1999; Baltic Astronomy 8, 171) is
implemented. Only main sequence stars (single and binary) are included.
• Satellite model:
• Attitude model: nominal scan law (L.Lindegren) and (simplified) satellite orbit
implemented.
• Geometric model of the Astro Focal Plane.
• Instrument model:
• Only Astro1 and Astro2 instruments are considered.
• A simple detection process is simulated in order to obtain the detection
parameters for each object.
• A bi-dimensional realistic PSF has been implemented (but does not include
chromaticity or focal plane position effects).
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GAIA SWG
Gaia Image and Basic Instrument Simulator
• Test the on-board algorithms
• Detection, Confirmation, Selection
• Compression
• Provide statistical results for GASS
• Focal plane optimisation studies
• Patches and samples
• Impact of CCD degradataion on final accuracy
• Reduction studies
• Image combining
• Calibration
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GAIA SWG
GIBIS Simulator
• Sources
•
•
•
•
•
All : ponctual, extended, fast moving objects
Statistical models
Special configurations
Time variation (variability, astrometry)
Observed images (HST)
• Instrument
•
•
•
•
All transits (scanning law)
All fields
On-board detection, selection, tracking
CCD details (noise,CTI, degradation…)
• Modular & easy to use
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GAIA SWG
GIBIS Status
• Development
 UML design, Java core, Iraf Image simulation
x Web page
• Instrument
 All instruments, Gaia2, Detection, PSF, Noise
x Scanning law, photometry, selection, tracking,
saturation, linearity, CTE, aging, RVS
• Universe
 Single, multiple stars, clusters, galaxies, HST image
x Time variation, cosmic-rays, solar-system objects
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GAIA SWG
Priorities & schedule
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GAIA SWG
Short term mission schedule
2001
2002
2003
GDAAS
2004
2005
Use of simulations for data
analysis preparation
Use of simulations for
mission/instrument
design
GAIA design
is frozen
Technology development
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Long term mission schedule
2005
2010
2020
2015
Use of simulations for data analysis preparation
Use of simulations for scientific exploitation preparation
Design, build, test
Launch!
Observations
Analysis
Catalogue!
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GAIA SWG
SWG priorities – immediate (2-3 months)
• Set up the Core Team: members!
You are invited to join
• Estimate manpower available and match it to needs/deadlines
• Coordination
 Packages & tasks, responsabilities
 Reference document to organise work
 Compilation of conventions, constants & reference terms
(use/complement GAIA-BCN-0??)
• Merging of GIBIS-GASS
• Take into account the new design of GAIA
• Provide acces to simulated data (web page?)
 Lists of objects
 Images
 Telemetry files
 GDAAS access (feasibility? DAWG)
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GAIA SWG
SWG priorities – short term (2002-2005) I
• Mission design
 Detailed testing of the capabilities of the revised GAIA design
 Simulations to complete Spectro design and evaluate its performance
 Telemetry & compression: final budget and trade-offs
 On-board data handling design
• Data analysis
 Database design optimisation
 Data processing (pipeline) design
o Ingestion
o Quick-look & initial classification
o Core processing (GIS)
o Spectro & photometry processing
 Query system & visualisation tools
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GAIA SWG
SWG priorities – short term (2002-2005)
II
• Scientific exploitation
 Estimation of GAIA performance for critical types of objects
Simulations for the development of specific algorithms for data
reduction.
 Other scientific aspects?
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GAIA SWG
SWG priorities – long term (2005 ) I
• Data analysis
 Data processing (pipeline) development & optimisation
o Ingestion
o Quick-look & initial classification
o Core processing (GIS)
o Spectro & photometry processing
 Shell processing
 Refined classification of objects
 Refine and expand query system & visualisation tools
 Interoperability with other large astronomical databases
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GAIA SWG
SWG priorities – long term (2005 ) II
• Scientific exploitation
 Produce simulated data allowing teams to prepare the exploitation of
GAIA data (through GAIA DB?).
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GAIA SWG
SWG initial schedule & milestones
• Immediate coordination activities
 Complete task list with names: April 2002
 Ref. document: May 2002
including schedule for 2002-2005 activities related to mission design
 Complete the merging of GIBIS & GASS: June 2002
• Integration activities
 Initial version of web page access to simulations: May 2002
 Agreed schema for integration of contributions: ??
 1st version of common tool box: ??
 Programming interface: ??
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GAIA SWG
DMS/PS simulations
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GAIA SWG
Object simulation: unification of the process
•The AstroObjects that form the ObservingList contain all the methods
needed to generate observations. This allows the unification of the
process even for very different types of objects.
Class
Extended Class
Method
AstroObject
Single Star
Multiple Star
NEO
Quasar ...
getPosition(time)
An unique Method with different implementations
(one for object type)
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GAIA SWG
Object simulation: SnapShots
• The simulation of objects is carried
out through the SnapShots.
• A SnapShot is a list of candidate
objects (of one or more types) to
be observed by an instrument
between two times (time1 and time2).
• Example: the SnapShot for the galaxy
model is formed by the objects (single
stars, binary stars,...) generated into
the HTM triangles crossed by the
FOV between time1 and time2.
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GAIA SWG
Crude simulation of Double Star / Planets
• Why ?
– Initially, to complexify the sky model in GDASS
– Now included in GASS/GIBIS
– Need to be complexified: to be used as a template
• Two Java classes
– Generation (dms_simu)
– Use (dms_orbit)
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GAIA SWG
I) Generation
• A call each time a star is created
• Randomly choose
– Number of companions
– Masses, down to EP
– Orbital elements
• Just needs as input:
– The absolute magnitude of the primary
– Optionally colour and mass of primary
• Simplistic assumptions
– Mostly based on Duquesnoy&Mayor 1991 for all stars
– Main-sequence assumed
– … needs something more realistic at a later stage
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II) Observations
• Computes the orbital effect at the given epoch
– getPosition(t)
• Simplistic hypothesis
– No interaction between companions
– No limb darkening, no mass transfer, etc…
• Astrometry
– Alpha, delta
– Distance
• Spectroscopy
– Radial velocity
• Photometry (if eclipsing)
– Light curve
– Light-time travel
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R CMa, eclipsing binary with a P=100yr companion
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GAIA SWG
Optimisations Needed
•
•
•
•
More realistic distribution of DMS/PS/BD
Evolved companions
Peculiar objects (contact binaries)
Variable companions
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GAIA SWG
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GAIA SWG
Backup slides
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GAIA SWG
Instrument models
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UML
The design and building of the GAIA simulator is a challenging task:
• Need for requirements & specifications to guide the development
• Many teams involved
• Management and coordination required
• Need to organise & control the source code
• Standarisation of tools, methods and interfaces is key for success
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GAIA SWG
The Unified Modelling Language (UML) was developed as a tool for
the design and management of software projects:
• Allows to specify, visualize and document a system under development
• Facilitates the collaboration between teams
• Allows a modular, iterative and incremental development
• Provides a common description tool, avoiding ambiguities in the design
of the system
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GAIA SWG
Java
• Object-oriented
• Really portable
• Allows a fast development
• Not too fast
• Not yet popular in the astronomical
community
• No numerical libraries available
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Programming languages
We propose to build the system around a Java core.
It is possible, with proper planning, to integrate algorithms & modules
written in any programming language.
However, this integration should be carefully planned and carried on
to ensure portability and to avoid a heavy load on the team in charge of
the integration.
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GAIA SWG
CVS
http://www.cvshome.org/
CVS is a version control system used to record the history
of the project source files
It allows a team of developers to simultaneously work in the
same set of source code files while avoiding the overwritting or
incompatibility of each other updates. CVS solves this problem
by insulating the different developers from each other. Every
developer works in his own directory, and CVS merges the
work when each developer is done.
At the same time, it ensures that each developer has the most
recent version of the files.
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GAIA SWG
CVS REPOSITORY
Reference version
of source files
CVS server
CVS client
CVS client
CVS client
CVS client
Local
version
Local
version
Local
version
Local
version
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